This invention relates to a cement additive and more particularly, to a cement additive used to improve the fluidity and appearance of strength of cement slurry, cement paste, mortar and concrete.
Various cement additives comprising polycarboxylic acid type copolymers have been proposed for enhancing the fluidity and flowability of concrete. While this works well for ordinary concretes, it is not so effective when high strength and high durability are required, as such copolymers tend to entrain an excess of air and retard setting.
In relation to pre-formed concrete products, it is strongly desired to decrease the total time spent in a form and to prevent defects when the form is removed. For such products, good appearance is also highly desirable, when the form is removed after steam curing. Various polycarboxylate materials to achieve this have been proposed, but none have been entirely satisfactory, causing such problems as retarded setting and low fluidity.
It has now been found that a cement additive containing a polycarboxylic acid type copolymer and a polyalkylene glycol derivative having a specific molecular structure can alleviate and sometimes completely remove all the above-mentioned problems, by having a high dispersing ability for various concretes, improving and retaining the fluidity of concrete, and also making it possible to increase the strength of pre-formed concrete, such that form removal after steam curing can be carried out relatively early, giving a product with low aeration.
The invention therefore provides a cement additive containing a polycarboxylic acid type copolymer and/or the salts thereof and a polyalkylene glycol derivative, said polycarboxylic acid type copolymer contains at least one species of copolymer, the monomers of which copolymer comprise at least an unsaturated polyalkylene glycol type monomer (A) and an unsaturated mono- or dicarboxylic acid type monomer (B).
The invention also relates to a cement additive, wherein the polycarboxylic acid type copolymers are copolymers which additionally include as monomer components an unsaturated polyalkylene glycol ester type monomer (C) and/or a monomer (D) polymerizable with the above-mentioned monomers (A) and (B), or with the monomers (A), (B) and (C).
The invention further relates to the above-mentioned cement additive, wherein the monomer (A) is a compound according to the general formula (1): 
wherein R1, R2 and R3 are each independently hydrogen or methyl, provided that not all are methyl; R4 is xe2x80x94CH2Oxe2x80x94, xe2x80x94(CH2)2Oxe2x80x94, xe2x80x94C(CH3)2Oxe2x80x94 or xe2x80x94Oxe2x80x94; the total carbon number of R1, R2, R3 and R4 is 3; R5O is one or more species of C2-C4 oxyalkylene groups, and in the case of two or more species may be block or random; R6 is hydrogen or a C1-C22 alkyl, phenyl or C1-C18 alkylphenyl group; p is an integer from on average 1to 100;
the monomer (B) is a compound according to the general formula (2): 
wherein R7 and R8 are each independently hydrogen or methyl; R9 is hydrogen, methyl or xe2x80x94(CH2)qCOOM2; R10 is xe2x80x94(CH2)rxe2x80x94; q and r are each independently an integer from 0 to 2; M1 and M2 are a monovalent metal, a divalent metal, ammonium or an organic amine;
the monomer (C) is a compound according to the general formula (3): 
wherein R11 and R12 are each independently hydrogen, methyl or (CH2)uCOOM3, u is an integer from 0 to 2, M3 is a monovalent metal, a divalent metal, ammonium or an organic amine; R13O is one or more species of C1-C4 oxyalkylene groups, and in the case of two or more species may be block or random; R14 is hydrogen or a C1-C22 alkyl, phenyl or C1-C22 alkylphenyl group; s is an integer from 0 to 2; t is an integer an average from 1 to 300; and
the monomer (D) is a compound according to the general formula (4): 
wherein R15, R16, R18 and R19 are each independently hydrogen or methyl, provided that not all are methyl, R17O is one or more species of C2-C4 oxyalkylene groups, and in the case of two or more species may be block or random; w is an integer an average from 1 to 300; v and x are each independently an integer from 0 to 2.
The invention also relates to the abovementioned cement additive, wherein the composition ratios of the monomers (A) and (B) in the polycarboxylic acid-type copolymers are 30-100 mole % based on the total mole amount of the monomers, and the average molecular weight of said polycarboxylic acid-type copolymer is from 3,000-100,000 (all molecular weights (MW referred to herein were measured by gel permeation chromatography with polyethylene glycol as standard).
The invention also relates to the abovementioned cement additive, wherein the average molecular weight of the polyalkylene glycol derivatives is from 1,000-100,000, in which the alkylene is one or more C2-C4 species, and the terminal groups of the polyalkylene glycol is hydrogen or a C1-C18 is alkyl or phenyl group.
Further, the invention relates to the abovementioned cement additive containing 100 weight parts of the polycarboxylic acid type copolymers and 10-50 weight parts of the polyalkylene glycol derivatives.
Also, the invention relates to the above mentioned cement additive, wherein the amount of the polycarboxylic acid type copolymers added to cement is 0.05-1.0% by weight based on the weight of cement, and the amount of the polyalkylene glycol derivative added to cement is 0.00-0.5% by weight based on the weight of cement.
Further, the invention relates to use of abovementioned cement additive in high strength concrete.
The invention also relates to the use of the abovementioned cement additive in the formation of pre-formed concrete articles by steam curing.
The invention further provides a method of preparation of a high-strength concrete mix, comprising the incorporation in the mix of a cement additive as hereinabove described.
The invention further provides a method of preparing of a concrete mix adapted to be used for the manufacture of articles by steam curing, comprising the incorporation in the mix of a cement additive as hereinabove described.
In a cement additive according to the invention, the monomers (A) are typically compounds according to the abovementioned general form (1), more specifically, the compounds in which 1-100 mole of an alkylene oxide is added to an unsaturated alcohol such as 3-methyl-2-buten-1-ol, 3-methyl-3-buten-1-ol, 2-methyl-3-buten-2-ol. One or more species of unsaturated alcohol may be used.
Examples of monomers (B) include compounds according to general formula (2), more specifically, for example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid and citraconic acid. One or more species of these may be used.
Monomers (C) are typically compounds according to general formula (3). Specific examples include unsaturated polyalkylene glycol monoester type monomers such as polyethylene glycol monoesters, polypropylene oxide monoesters, monoesters of polyethylene glycol/polypropylene oxide copolymers, derivatives in which a terminal hydrogen of these glycols is etherified, and the like, such as triethylene glycol monoacrylate, polyethylene glycol (MW 200) monoacrylate, polyethylene glycol (MW 400) monoacrylate, polyethylene glycol (MW 600) monoacrylate, polyethylene glycol (MW 1000) monoacrylate, polyethylene glycol (MW 2000) monoacrylate, polyethylene glycol (MW 4000) monoacrylate, polyethylene glycol (MW 6000) monoacrylate, triethylene glycol monomethacrylate, polythylene glycol (MW 200) monomethacrylate, polyethylene glycol (MW 400) monomethacrylate, polyethylene glycol (MW 600) monomethacrylate, polyethylene glycol (MW 1000) monomethacrylate, polyethylene glycol (MW 2000) monomethacrylate, polyethylene glycol (MW 4000) monomethacrylate and polyethylene glycol (MW 6000) monomethacrylate, and one or more species of these may be used.
The monomers (D) are typically compounds according to general formula (4), specific examples including unsaturated polyalkylene glycol diester type monomers and/or styrene, styrenesulfonic acid and/or the salts thereof acrylic acid alkyl esters (alkyl of C22 maximum) methacrylic acid alkyl ester (alkyl of C22 maximum), maleic anhydride, maleic acid monoesters (akyl of C22 maximum), and/or alkylene glycol of C3 maximum and 1-300 alkylene glycol units, maleic acid diester (alkyl of C22 maximum and/or alkylene glycol of C3 maximum and 1-300 alkylene glycol units, vinyl acetate, acrylamide and acrylamide methylpropansulfonic acid and/or the salts thereof.
Specific examples include styrene, styrenesulfonic acid and/or the salts thereof, acrylic acid methyl ester, acrylic acid ethyl ester, acrylic acid butyl ester, methacrylic acid methyl ester, methacrylic acid ethyl ester, methacrylic acid butyl ester, maleic anhyride, maleic acid methyl monoester, maleic acid ethyl monoester, maleic acid methyl diester, maleic acid ethyl diester, vinyl acetate, acrylamide, acrylamide methylpropansulfonic acid and/or the salts thereof, methallyl sulfonic acid and/or the salts thereof. One or more species of these may be used.
Specific non-limiting examples of polycarboxylic acid type copolymers are those described in JP, A, H5-306152, JP, A, H6-211949, JP, A, H9-286647 and JP, A, H10-236858.
The composition ratio of the monomers (A) and (B) in the polycarboxylic acid type copolymers in the invention to total amount of the monomers is preferably 30-100 mole %, and the average molecular weight is preferably 3,000-100,000.
In the polyalkylene glycol derivatives of the invention, the average molecular weight is 1,000-150,000, preferably 1,000-100,000, more preferably 4,000-50,000, the alkylene is one or more C2-C4 species, and it may be block or random in the case of 2 or more species, the terminal groups of polyalkylene glycol are hydrogen, C18 maximum alkyl or phenyl groups.
In a cement additive of the invention, the preferred proportions are 100 weight parts of polycarboxylic acid type copolymers and 10-50 weight parts of polyalkylene glycol derivatives.
A cement additive of the invention is preferably used in such a quantity that polycarboxylic acid type copolymers are present in the proportion 0.05-1.0% by weight based on cement weight and polyalkylene glycol derivatives are present in the proportion 0.005-0.5% by weight based on cement weight. However, the amount of the cement additive according to the invention to be used can be appropriately determined according to a cement composition used, it basically being the amount which is necessary to attain the desired strength development and improved time to form removal after steam curing, and it is possible that suitable proportions outside these limits may be found.
A cement additive according to the invention may be used for stiff consistency concrete, plastic concrete, high fluidity concrete, high strength concrete, cement paste as generally used, mortar, grout, concrete and the like, although the beneficial effects of the invention are most noticeable in high strength concrete in which the water/cement ratio is low.
A cement additive according to the invention may be mixed, if desired, with other additives to expand its versatility. Typical examples of other additives are conventional water reducing agents (lignosulfonate, oxycarboxylate, polyalkylsulfonate, polycarboxylate), air content-regulating agents, drying shrinkage reducing agents, accelerators, retarders, foaming agents, anti-foaming agents, anti-rust agents, set acceleration agents, high early-strengthening agents, efflorescence-inhibiting agents, bleeding inhibitors, pumping aids, and water-soluble polymers.
A cement additive according to the invention exhibits a high dispersing ability of a degree never obtained by use only of polycarboxylic acid-type copolymers to various concretes such as ordinary concrete, high strength concrete and steam curing concrete. Without restricting the scope of the invention in any way, it is believed that this is the result of a synergistic effect of the polycarboxylic acid type copolymers and the polyalkylene glycol derivatives. It both enhances the fluidity of concrete and maintains this fluidity, thereby making it possible to increase the strength development and decrease the time for form removal after steam curing. The latter is particularly valuable in that it permits economies such as the reduction of time spent in a form used and the reduction of defects in concrete products manufactured in a concrete factory.
The invention is now further illustrated by the following non-limiting examples wherein are used the cement additives containing polycarboxylic acid type copolymers and polyalkylene glycol derivatives according to the invention.